1. Field of the Invention
The present invention relates to earth boring drill bits and specifically, to such bits formed with cast matrix material of a hard wear resistant material.
2. Description of the Prior Art
Diamond "matrix" drill bits are known in which a metallic mandrel has bonded thereto a matrix body of tungsten carbide. The matrix is formed or "cast" by allowing molten metal to infiltrate a body of discrete tungsten carbide in a suitable mold. The matrix body of the bit can have diamonds which are arranged to define cutting edges on the external surface of the bit body. Certain of the prior art bits have been formed with a bit body of generally conical cross-sectional area and having blades which extend axially and radially outward from the bit body to form flat, wing-like projections extending outwardly from the bit face. Typical prior art bits have embodied blades which have extended as much as about 11/2 inches from the bit body. Greater blade exposure resulted in gross failure due to unsupported matrix fracture.
The present invention has as its object, the provision of a matrix bit which makes possible the economical use of case tungsten carbide and which provides cast matrix bits having blades with greater standoff from the bit body than was previously possible.